1. Field of the Invention
This invention relates to a driving state-monitoring apparatus for automotive vehicles, which monitors the driving state of the driver of the automotive vehicle, and gives an alarm, if necessary.
2. Prior Art
Conventionally, a driving state-monitoring apparatus has been proposed e.g. by Japanese Laid-Open Patent Publication (Kokai) No. 5-85221, which estimates a delay in response of a driver of an automotive vehicle and the difference between the actual position of the vehicle and a lane on which the vehicle is traveling (reference position of the vehicle in the lane), based on an amount of steering of the vehicle performed by the driver and the vehicle speed, and compares the estimated delay in response and the estimated difference with respective reference values to be assumed during normal driving states of the driver, to thereby check the driving state of the driver e.g. for abnormal steering caused by a doze or lowered driving ability of the driver resulting from his fatigue.
However, since the proposed driving state-monitoring system calculates or estimates the difference between the actual position of the vehicle and the lane on which the vehicle is traveling (reference position in the lane), based on the amount of steering of the vehicle performed by the driver and the vehicle speed, but not based on physical amounts directly related to behavior of the vehicle. As a result, an error can be produced in the calculated difference due to conditions of the road surface (e.g. irregularities and gradient of the road surface), a difference in driving skill between individual drivers (e.g. between a beginner and a skilled driver), and so forth, which results in degraded accuracy of determination of the driving state of the driver.